Multi-objective collaborative optimization of internal thread cold extrusion process based on response surface method

For the purpose of improving the forming quality of cold extrusion internal thread and investigating the interactive effects of distinct process parameters on the forming quality of internal thread, this article established a regression response model between the influencing factors and optimization objectives by using the response surface experiment analysis method, and obtained the interactive effects of the bottom hole diameter, the extrusion speed and the coefficient of friction on the extrusion torque, extrusion temperature, and tooth height rate. The objective function was optimized using the regression model to obtain the optimal combination of parameters (bottom hole diameter 7.34 mm, extrusion speed 30 r/min, and friction coefficient 0.11). For the purpose of verifying the feasibility and validity of the theoretical model and the optimized design, internal thread extrusion experiments are carried out under the optimal combination parameters. The experiment results show that the extrusion torque is 3.17 N m, the extrusion temperature is 79.8 degrees C, and the tooth height rate is 77.23%, and the error with the predicted value is 8.56%, 2.57%, and 5.27%, respectively, which further demonstrates the accuracy of the model.